Rectifier.



H. K. SANDELL.

RECTIFIER.

APPLICATION FILED MAY 1, 19M.

1,238,443. Patented Aug. 28, 1917.

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RECTIFIER.

APPLICATION FILED MAY 1. 1914.

Patented Aug. 28, 1917.

3 SHEETS-SHEET 3- UNITED STATES ATENT. OFFICE.

HENRY K. SAN'DELL, OF CHICAGO, ILLINOIS, ASSIGNOB T0 HERBERT S. MILLS, OF CHICAGO, ILLINOIS.

RECTIFIER.

' Specification of Letters Patent.

Patented Aug. 28, 1917.

Application filed Kay 1, 1914. Serial No. 835,644.

To all whom it may concern:

Be it known that I, HENRY K. SANDELL, a citizen of the United States, residing at Chicago, in' the county of Cook and State of Illinois, have invented a new and useful Improvement in Rectifiers, of which the following is a specification.

My invention relates to certain new and useful improvements in rectifiers and 1s fully described and explained in the specification and shown in the accompanying drawings, in which:

Figure 1 is a side elevation of my 1mproved device; Fig. 2 is an end view from the left of Fig. 1; Fig. 3 is an end view looking in the opposite direction showing the alternating-current brushes; Fig. 4 is a section on the line 4 of Fig. 1; Fig. 5 is a section through the stator on line 5 of Fig. 4, and Fig. 6 is a circuit diagram.

Referring to the drawings, 7 generally indicates the stator which may be of known type and is here shown of the ordinary induction type. Mounted within the stator is the rotor 8 carried by a shaft 9. The rotor is provided with pole-pieces of the usual radial form, upon which are wound two coils 8 and 8", the'coils 8 being hereinafter designated as the shunt rotor coils, and the coil 8 being of much heavier wire and hereinafter designated as the series rotor coils. The rotor is also provided with slip-rings 10 and 11 through which alternating cur rent may be led in from brushes provided for the purpose. A starting device is also provided, this consisting of a centrifu al conducting piece 12having connection with the slip-ring 11 and adapted to contact with a pin 13 insulated from the slip-ring 11 and connected to the starting-coils, which are indicated at 14. After the rotor gets in motion the piece 12 moves away from the pin 13 to break the circuit through the starting coils.

The parts thus far shown and described (with the exception of the series rotor coils 8 it will be seen, are those of the common induction motor in which the current is led to the rotor through slip-rings, and the stator carries the induced currents. This type of motor is highly advantageous for use in a rectifier of small size because it is very cheap and is thoroughly practical for small-sized devices. In using the device, however, for rectifying purposes, it must be got into step and remain in step and, therefore, in some manner it becomes necessary to eliminate the slip which is the characteristic of induction motors. In other words, the induction motor must be made to run synchronously. This is accomplished by inserting into the field or stator twocoils 15 in series with each other and so wound as to produce localized fields of opposite polarity, which coils 15 are excited by the rectified current produced as hereinafter specified, being in shunt with the main leads therefrom. These coils are supplemented in the manner and for the purpose hereinafter explained.

The shaft at the left of the rotor is hollowed out to receive conductors 16 which carry the unrectified current. The series rotor coils 8 are in series with these conductors 16, that is, the circuitruns from the slip-ring 11 through the series rotor coils to one of these conductors, from which it flows through a commutator hereinafter to be described and any translator receiving current therefrom, thence back to the commutator and through conductors 16 to the slip-ring 10. The shunt rotor coils, on the other hand, are in shunt with the conductors 16,

the current which flows thereto branching oil from the main circuit leading from the slip-rings as shown in the drawings. On the end of the shaft is a disk 17 carrying four commutator segments 18 and 19, the correspondingly numbered segments being electrically connected together, while the two conductors 16 are respectively connected to the two pairs of commutator segments, so that each has connection with two opposite segments. Bearing upon the commutator segments are four brushes 20 and 21 90 apart, the opposite and correspondingly numbered brushes being electrically connected. This construction is such that the rectified current flowing in one direction is divided between the two commutator segments and brushes of each pair whereby the effective surface is made large.

For the purpose of supplementing the action of the synchronizing coils heretofore described, and particularly for the purpose of assuring synchrony with low voltage currents, I provide two additional coils 22 in the stator, similar in construction and position to the coils 15 but wound with rela tively heavy wire and placed in series with the leads which carry away the rectified currents from the brushes. Reference to Fig. 6 will show that one of the brushes 20 is connected to one of the line wires which is shown as supplying current to a translator, such as the motor 23, while one of the brushes 21 leads through the stator coils 22 and thence to the opposite line wire leading to the translator.

It is believed that the operation of the device will be readily apparent from the description of its construction. The alternating current is led in through the brushes on the slip-rings 10 and 11, energizing the main and starting coils of the rotor. When tho rotor is up to speed, which is nearly a synchronous speed, the slip being naturally very small, the current led out of the brushes bearing on the commutator segments will alternate only very slowly. It will obviously alternate only as often as the slip amounts to 'a quarter turn of the rotor. During any one of the periods of flow of the current thus issuing from the commu tator brushes, the coils 15 and 22 in the stator can become energized and establish localized poles in the stator, so that thereafter the rotor will run synchronously and the direct current can be continuously drawn from the commutator brushes and utilized in any desired manner as, for instance, in the motor which is shown diagrammatically in Fig. 6 as having connection therewith. Of course, as soon as the rotor is moving at a sufilciently high speed, its starting coils are cut out in the usual manner.

The provision of the series rotor coils is advantageous in adapting the device to use with extremely low voltages, and fitting it to withstand excessive changes in voltage without getting out of step. These coils are of very low resistance relative to the shunt coils and under normal conditions the main magnetic effect is produced in the rotor by the shunt coils.

The mechanical structure here shown is very simple and is peculiarly designed for rectifying currents of relatively small volume. The motor is, or may be, of a type commonly sold on the market at a very low price, varied only by the introduction of coils into its stator and rotor. It requires no material modification except the addition of these coils and the provision of the commutator at one end.

In the motor selected the rotor is the part affected by the alternating current because, by such construction, the necessary number of movable parts is reduced to the minimum.

I realize that considerable variation is possible in the details of the construction herein shown, and I do not intend to limit myself thereto, except as pointed out in the following claims, in which it is my intention to claim all the novelty inherent in the device as broadly as is permitted by the state of the art.

I claim as new and desire to secure by Letters Patent:

1. In combination with a stator of the induction type and field windings therein, a rotor, series and shunt coils thereon, sliprings and a commutator carried by the rotor, connections between the slip-rings and commutator segments in which the series rotor coil is in series and with which the shunt rotor coils are in shunt, and a second coil in the stator in series with the direct current leads which conduct the rectified current.

2. A device of the character described, comprising a magnetizable rotor, series and shunt coils thereon, slip-rings and commutator segments carried by the rotor, connections between the slip-rings and commutator segments, the series-rotor coil being in series with one of said connections and the shunt rotor coils being in shunt therewith, an inductive stator surrounding the rotor, a winding in the stator, connections between the commutator brushes and the stator winding, and a second coil in the stator in series with the direct current leads which conduct the rectified current.

3. A device of the character described, comprising a magnetizable rotor, shunt and series coils thereon, slip-rings and commutator segments carried by the rotor, connections between the slip-rings and commutator segments, the series-rotor coils being in series with one of said connections and the shunt rotor coil being in shunt therewith, a stator surrounding the rotor and a synchronizing coil mounted in the stator and receiving current from the commutator brushes, and a second coil in the stator in series with the direct current leads which conduct the rectified current.

4. A device of the character described having primary and secondary members, one of which is a rotor and the other a stator, shunt and series coils in the primary member to receive alternating current, a commutator, one member of which is driven by the rotor, connections for leading the alternating current to one of the commutator members in shunt with the shunt coil and through the series coil of the primary member, three In testimony whereof I have hereunto set windings in the secondary member, one of my hand and aifixed my seal this 22nd day 10 wfhicllli1 ils1 short ciiirclited aind 1{he other two of April, 1914.

o w 'c areint e orm o 00' s, connections from the other commutator member for lead- HENRY SANDELL ing ofi direct current one of the two coils In presence of two subscribing witnesses:

in the secondary member being in shunt and A. J. FLOYD,

the other in series with said connections. Nnmm B. DEARBORN. 

